1. Field of the Invention
The present invention relates to a jet-propelled boat, equipped with a jet pump with a rotatable nozzle as a means of propulsion. The present invention more specifically relates to a jet-propelled boat, which is able to change course even when the jet stream from a jet pump is stopped or weak.
2. Description of the Relevant Art
Jet-propelled boats are well known, such as in Japanese Patent Laid-open Publication No. Hei. 5-162689. As shown in FIG. 5, a boat 1, in accordance with the background art, is equipped with an engine 3 mounted within a boat body 2. A jet pump 3a is driven by the engine 3. A nozzle 5 that can be rotated right or left, via a pair of upper and lower pins 6, is provided at a jet opening 4 of the jet pump 3a.
A rudder 8 is provided at a shaft 9 at a rear part of the nozzle 5. The nozzle 5 is connected to handlebars 7 using a steering wire (not shown) and is rotated by operating the handlebars, so that the rudder 8 and the nozzle 5 rotate together.
According to this jet-propulsion boat, the course can be changed while the boat is being propelled by a jet stream from the jet pump 3a by rotating the nozzle 5 so as to change the direction of the jet stream. When the boat's engine is either stopped or decelerating, the jet stream of the jet pump is stopped or is weak. Even so, the course of the boat 1 can be changed using the rudder 8, while the boat is advancing as a result of its own inertia. If the rudder 8 is not provided with this type of jet-propelled boat, the course cannot be changed when the boat is travelling under its own inertia. Therefore, the rudder 8 is advantageous in allowing steering of the boat when the boat's engine is either stopped or decelerating.
With the jet-propelled boat of FIG. 5, the construction is such that the course of the boat is changed by changing the direction of a water flow W moving along the boat bottom 2a using the rudder 8. Therefore, in accordance with the background art, a lower end 8a of the rudder 8 must project further downwards than the boat bottom 2a, in order to function as a rudder. This results in a requirement that the boat not be used in shallow water, since the rudder 8 could be damaged upon contact with the water's bottom. When the center of rudder force and the rudder shaft become separated, the steering force required for the rudder to be effective increases dramatically.